Fluoroacetic acids



and to a process of producing them.

PatentedMar. 20, 1945 UNITED STATES PATENT oFFlcE FLUOROAOETIC ACIDS Albert L. Henne, Columbus, Ohio, assignoi' to E. I. du PontdeNemours &'C'ompa.ny, Wilmington, Del., a corporation of Delaware No Drawing. Application May 19, 1943.

Serial No. 487,615

8 Claims. (Cl. zoo- 539) A. This invention relates to fiuoroacetic acids B. Swarts, in the latter part of the nineteenth century, prepared certain fiuoroacetic acids, the

preparation of which is described in Memoirs Belgique.

. par. l'Academie Royale Other investigators have surveyed this field this field but until recently the best available process for the preparation of tri'fiuoroacetic acid was the acid oxidation of meta-amino-benzo'trifiuoride, a process which is long, costly, and gives but small yields of the acid.

0. It is an object of this invention to' make iluoroacetic acids, particularly diand trifiuoroacetic acids, by a process which is technically and economically satisfactory.

D. These objects are accomplished, generally speaking, by reacting compounds of the type CF2XCY :CYZ. in which Y and Z are hydrogen or halogen, and X is hydrogen, fiuorine or chlorine, with an alkali metal permanganate in alkaline medium, preferably potassium permanganate in aqueous solution made alkaline by sodium hydroxide.

E. Inthe'practice of the invention intermediatescorresponding to the formula above are used. The prime requirement of the compound is that it shall contain the grouping -CFzCY=CYZ, Y

and Z being hydrogen or halogen. Specificexamples of compounds containing this group will ,be found hereinafter in this specification.

F. In carrying out the reaction the temperature of the reaction mass.is raised enough to produce an efficient reaction without carrying off the reactants or inducing excessive side reactions. In general, I have found temperatures of the order of 70-80 C. to be quite satisfactory.

as ethyl alcohol or ethers.

is inert to the ingredients of the reaction mass Temperatures from 20-130 have been employed with particular reactants. At temperatures above 100, pressure vessels can be used and the permanganate and caustic can be addedsimultaneously and slowly to the higher boiling organic starting materials.

G. The reaction, ingeneral, may be carried out at atmospheric pressure, although other pressures, either higher or lower, may be used where efiiciency is served.

H. When the reaction has been completed, excess caustic can be neutralized with acid, such as hydrochloric acid. If, after the reaction has been completed, there is an excess of potassium permanganate, it can be removed by reaction with sulfur dioxide or bisulfite. In working up the oxidation mass the alkali salt of the organic acid can be isolated by clarification, to rid it of MnOz;

and evaporation to dryness. Alternatively, the oxidation mass can be acidified, the aqueous organic acid may be distilled off, neutralized with sodium carbonate, dried as the sodium salt, mixed 'with the theoretical amount or an excess of 93- sulfuric acid, and the organic acid distilled ofi.

1. Present observations seen to indicate that a combined hydrolysis and oxidation occurs, according to a net reaction which may be expressed as follows when CFsCCl==CCIz is the intermediate:

The trifiuoro acetic acid is formed from the potassium salt by reaction with acid. Extraction of the acid is accomplished by solvents, such Any solvent which vention but are not intended to be a limitation thereof.

Example I ,100 parts of CF3CCl=CCl2 (Henne and Whaley, JACS 64, 1158) were charged to a fiask fitted with a separatory funnel, a stirrer, a reflux condenser and a thermometer, 200 parts of water were added forming a layer above the intermediate. parts of potassium permanganate were added with enough sodium hydroxide to maintain slight alkalinity at all times. The mixture was heated with agitation to 80 C. for a period of 40 hours. When the oxidation was complete,

the charge was made neutral by the addition of a small quantity of HCl. The clear liquid, which contained the sodium and potassium salts of trifiuoro acetic acid in aqueous solution, was decanted oif. The mixture was filtered and washed with warm water, the filtrate and wash liquor being combined with the decanted liquor and evaporated to dryness. The sodium and potassium salts of trifiuoro acetic acid were extracted from the mixed solids resulting from the evaporation to dryness by dissolving them in ethyl alcohol and filtering. The alcohol was removed from theyflltrate by distillation and the dry salt or trifiuoro acetic acid-was treated with sulfuric acid. The free trifluoro acetic acid was then distilled 'ofi. A yield of75% of. theory was obtallied.

Y 4 .Emmple II I If' 1,1,2,3 tetrachloro-3,3-difluoropropene-1 is substituted for the 1,1,2-trichloro-3,3,3#trifluoropropene-l which was-used in Example 1 and the reaction is'otherwise carried out similarly. monacetic acid isobtain'ed. 1

chloro-difluoro Example II I i 1. part. of CFaCH=CH2 (Henne & Whaley, J. A 3 Il -I of potassium permanganate, 2.0 parts'of" hydroxide, and 3.0 x' parts of water were sealed 'ina glass tube. The

tube was agitated for two days at'25-30 C; The tube was opened and the contents. extracted'with a water to separate soluble salts from manganese dioxide.- The resulting solution: was then neutralized with dilute HCI; dried on the steam bath and the cake extracted with absolute alcohol to separate the salt of trifiuoro acetic acid from the inorganic salts present. The alcohol extract was and was maintained at 68 by using a cool aerate-z Iclaim:

LThe process of preparing trifluoro acetic I acid which comprises reacting CFaCC1=CClz with permanganate in aqueous alkaline medium at about 80 0., neutralizing; removing the solution from the solids, evaporating the solution t dryness, extracting the dried. residue with alcohol,

. separating the extract-from thealcohol, reacting Water bath and controlling the rate of addition of difluoride. After about three hours at 68-70", the reaction was virtually complete and the mass was allowed to agitate until. the temperature dropped to then was heated to 85 until no more refluxing was observed. The oxidation mass was then cooled, excess of permanganate destroyed by sulfur dioxide, and the mass slowly acidified by sulfuric acid (220 parts). Sulfur dioxide was then passed in with external cooling untilthe manganese dioxide dissolved. A further 184 parts of concentrated sulfuric acid were carefully added, the mass cooled, and difluoro acetic acid extracted by continuous extraction for 30-40 hours with diethyl ether. Distillation of the solvent and product through an 18-inch Vigreaux column gave difluoro acetic acid in 85% (theory) yield. The product (difluoro acetic acid) was a clear colorless sharp-smelling liquid which fumes in moist air.

K. An advantage of the invention is in providing technically feasible methods for preparing diand trifluoro acetic acids. Other methods are in comparison technically undesirable and too expensive.

L. As many apparently widely different em- I bodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

- acetic acid by distillation. I

tillation.

it with sulfuric acid, and separating 'trifluoro 2. The process of preparing difluoro acetic acid which comprises reacting CHFaCCl=CHCl with a permanganate in aqueous alkaline medium at about 70 C., destroying excess permanganate by v reaction with S02, neutralizing the mass and reacting the, prime product with sulfuric acid, ex-

tracting the prime product. from the mass with diethyl ether, and removing the extract by dis- 3-. The process ofpreparing a fluoro acetic acid which comprises reacting a compound-represented by the formula CF2XCY=CYZ (in which each of Z,.Y and X is one of a group consisting of hydrogen, fluorine, and chlorine) with a permanganate I in an aqueous solution of caustic alkali at a tern.-

perature of from about 70 C. to about 80 C.,

neutralizing the reaction mass and reacting it I with mineral acid, extracting the prime. product with a solvent, andisolating the prime product y from the solvent.

4. The process of preparing a fluoro acetic acid which comprises reacting a compound represented by the formula CFzXCY- CYZ (in which each of Z, Y and)! is one of a group consisting of hydrogen, fluorine, and chlorine) with an alkali metal permanganate in an aqueous solution of caustic alkali at a temperature of from about 70 C. to about 80 C., and recovering the fluoro acetic acid from the reaction mass.

5. The process of preparing a fluoro acetic acid which comprises reacting a compound represented by the formula CFzXCY=CYZ (in which each of Z, Y and X is one of a group consisting of hydrogen, fluorine, and chlorine) with a permanganate in an aqueous alkaline medium at a temperature of from about 25 C. to about 80 C. and isolating the fluoro acetic acid.

6. The process of preparing a fluoro acetic acid which comprises reacting a compound represented by the formula CF2XCY=CYZ (in which each of Z, Y and X is one of a group consisting of hydrogen, fluorine, and chlorine) with a permanganate in an aqueous alkaline medium at a. temperature .of from about 25 C. to about C., neutralizing the reaction mass and reacting it with mineral acid and isolating the fluoro acetic acid.

'I. The process of preparing trifiuoro acetic acid which comprises reacting CF3CC1=CC12 with an alkali metal permanganate in an aqueous solution of caustic alkali at about 80 C. and recovering the trifluoro acetic acid from the reaction mass.

-8. The process of preparing difiuoro acetic acid which comprises reacting CHFzCC1=CHC1 with an alkali metal permanganate in an aqueous solution of caustic alkali at about 70 C. and recovering the difluoro acetic acid from the reaction mass.

AL ERT L. HENNE. 

